title: T-shaped ionic liquid crystals based on the imidazolium motif: exploring substitution of the C-2 imidazolium carbon atom.
abstract: In this contribution the first examples of so-called rigid-core, T-shaped imidazolium ionic liquid crystals, in which the C-2 atom of the imidazolium ring is substituted with an aryl moiety decorated with one or two alkoxy chains, are described. The length of the alkoxy chain(s) was varied from six to eighteen carbon atoms (n=6, 10, 14-18). Whereas the compounds with one long alkoxy chain display only smectic A phases, the salts containing two alkoxy chains exhibit smectic A, multicontinuous cubic, as well as hexagonal columnar phases, as evidenced by polarising optical microscopy, differential scanning calorimetry, and powder X-ray diffraction. Structural models are proposed for the self-assembly of the molecules within the mesophases. The imidazolium head groups and the iodide counterions were found to adopt a peculiar orientation in the central part of the columns of the hexagonal columnar phases. The enantiotropic cubic phase shown by the 1,3-dimethyl-2-[3,4-bis(pentadecyloxy)phenyl]imidazolium iodide salt has a multicontinuous Pm ̄3m structure. To the best of our knowledge, this is the first example of a thermotropic cubic mesophase of this symmetry.
authors.affiliation: Katholieke Universiteit Leuven, Department of Chemistry, Celestijnenlaan 200F (PO Box 2404), 3001 Heverlee, Belgium. karel.goossens@chem.kuleuven.be
authors.forename: Karel
authors.initials: K
authors.lastname: Goossens
authors.forename: Sil
authors.initials: S
authors.lastname: Wellens
authors.forename: Kristof
authors.initials: K
authors.lastname: Van Hecke
authors.forename: Luc
authors.initials: L
authors.lastname: Van Meervelt
authors.forename: Thomas
authors.initials: T
authors.lastname: Cardinaels
authors.forename: Koen
authors.initials: K
authors.lastname: Binnemans